Propellers that are used to provide thrust for platforms such as airplanes, have a blade angular setting or pitch that can be fixed for variable speed systems or variable for variable pitch constant speed systems. In variable speed systems, blade pitch is used to control engine speed. Thrust is varied by adding more fuel, which increases torque to the propeller, thereby increasing its speed. Blade pitch is then increased to reduce speed to the desired value while simultaneously increasing thrust. Fixed pitch propellers have a constant angular position and require engine speed changes to change thrust. When fuel is added, the engine speed increases and the thrust from the propeller increases.
The drawback for variable pitch propellers is that the variable pitch mechanisms are complicated and add weight. Known apparatus for varying a blade pitch include using mechanical actuators and linkages connected to the propeller blades. Such known apparatus are complex to design and set up and require constant operation to maintain engine speed control. When using such known actuators, if the mechanical actuator fails, the blade pitch and, thus, the engine speed are no longer controllable. The disadvantage of a fixed propeller is that the optimum performance is compromised because the design point is fixed at a particular engine speed, forward speed, and engine power level. These conditions happen at only one flight condition.